Flight of the Navigator is an older movie(1978) that many young people have never seen. However, this is a movie I grew up watching. Until recently, I have never paid attention to movie physics. In Flight of the Navigator, a boy named David meets a computer being named Max who is also the spaceship. In the movie, there are numerous flights in which David speeds up and stops almost instantly. David even goes on to fly more than 500 light years in a couple of hours, eventually coming home to his family 10 years older.
There is a particular scene in the movie where David flies up above the earth in about 5.5 seconds, and comes back down in the same amount of time. Here is the scene:
I have estimated that the distance he traveled was about 321km. In the scene, David says to take him 20 miles away, but Max the spaceship takes him much further. Using distance/time, I found that he is moving at about 58.4km/second. This is very, very fast, in fact faster than the ISS’s orbit speed! Standing on the earth you experience one g, but in his flight he would experience 5,960 g’s of force. I converted 58.4km/second into meters/second, and then divided the number by 9.8meters/second squared to find the g's he would experience. With no suits or equipment, people tend to black out at about 5-6 g’s. When David arrives in space, he is well awake and yelling to go back down to earth, where realistically, he should probably be dead because his blood would rush away from his brain while going up, and vice versa going back down. This is a violation of human limits. In the scene, when David is flying upwards, he does experience some force. His speech is slurred and his arms are stuck to the seat, but it is not as much g-force as he should have experienced.
I also ask, how does David not splat into the walls of the spaceship because of inertia? The law of inertia says that an object will want to keep moving in a straight line until acted on by another force, therefore he should slam into ceiling when the spaceship comes to a stop in space. If you were driving at 70mph in your car with no seat belt and slammed into a wall, causing your car to stop, you would go flying out the windshield because of inertia. David's body will want to keep moving forward too, until he collides with the ceiling when the spaceship stops in space, and then the floor when the spaceship stops on earth. This leads me to the next question: how much force should David feel when he (should) slam into the walls of the spaceship when it stops? Will he survive the collision with the walls? There is no seat belt to stop him from flying around. Seat belts stop you from wanting to keep moving because of inertia. Because David has no seatbelt to stop him from flying around, he should experience the full reign of his force when colliding with the walls. I have estimated that David weighs about 50kg for the purpose of using the equation F=ma. Though it looks like the spaceship takes off and stops instantly, I will just assume that there is acceleration. Dividing 58.4km/second by 5.5 seconds leaves his acceleration at about 10km/second squared. David should experience 2.92x10^6N's of force when slamming into the ceiling and floor. It takes about 4,000N to break human bones, and this is more than enough force to crush a human flat.
This movie violates the law of inertia and pushes David well over the threshold of survivability. The force he experiences in terms of g and in splatting into the wall should leave him dead. Though this is a great classic movie, the directors totally neglected general laws of physics in this scene and much of the movie.